Department of Civil and Environmental Engineering, University of California , Los Angeles, California 90095, United States.
Environ Sci Technol. 2016 Sep 6;50(17):9599-607. doi: 10.1021/acs.est.6b02797. Epub 2016 Aug 17.
This study investigated the impacts of individual chlorinated solvents and their mixtures on aerobic 1,4-dioxane biodegradation by Pseudonocardia dioxanivorans CB1190. The established association of these co-occurring compounds suggests important considerations for their respective biodegradation processes. Our kinetics and mechanistic studies demonstrated that individual solvents inhibited biodegradation of 1,4-dioxane in the following order: 1,1-dichloroethene (1,1-DCE) > cis-1,2-diochloroethene (cDCE) > trichloroethene (TCE) > 1,1,1-trichloroethane (TCA). The presence of 5 mg L(-1) 1,1-DCE completely inhibited 1,4-dioxane biodegradation. Subsequently, we determined that 1,1-DCE was the strongest inhibitor of 1,4-dioxane biodegradation by bacterial pure cultures exposed to chlorinated solvent mixtures as well as in environmental samples collected from a site contaminated with chlorinated solvents and 1,4-dioxane. Inhibition of 1,4-dioxane biodegradation rates by chlorinated solvents was attributed to delayed ATP production and down-regulation of both 1,4-dioxane monooxygenase (dxmB) and aldehyde dehydrogenase (aldH) genes. Moreover, increasing concentrations of 1,1-DCE and cis-1,2-DCE to 50 mg L(-1) respectively increased 5.0-fold and 3.5-fold the expression of the uspA gene encoding a universal stress protein. In situ natural attenuation or enhanced biodegradation of 1,4-dioxane is being considered for contaminated groundwater and industrial wastewater, so these results will have implications for selecting 1,4-dioxane bioremediation strategies at sites where chlorinated solvents are present as co-contaminants.
本研究考察了个体氯代溶剂及其混合物对 Pseudonocardia dioxanivorans CB1190 有氧降解 1,4-二恶烷的影响。这些共存化合物的关联表明，在考虑它们各自的生物降解过程时需要重要的考虑因素。我们的动力学和机制研究表明，单个溶剂对 1,4-二恶烷生物降解的抑制作用依次为：1,1-二氯乙烯（1,1-DCE）>顺-1,2-二氯乙烯（cDCE）>三氯乙烯（TCE）>1,1,1-三氯乙烷（TCA）。5mg/L 的 1,1-DCE 的存在完全抑制了 1,4-二恶烷的生物降解。随后，我们确定了 1,1-DCE 是细菌纯培养物暴露于氯代溶剂混合物以及从受氯代溶剂和 1,4-二恶烷污染的地点采集的环境样品中，对 1,4-二恶烷生物降解抑制作用最强的化合物。氯代溶剂对 1,4-二恶烷生物降解率的抑制归因于 ATP 产生延迟和 1,4-二恶烷单加氧酶（dxmB）和醛脱氢酶（aldH）基因下调。此外，将 1,1-DCE 和 cis-1,2-DCE 的浓度分别增加到 50mg/L 时，编码普遍应激蛋白的 uspA 基因的表达分别增加了 5.0 倍和 3.5 倍。地下水和工业废水中正在考虑原位自然衰减或增强 1,4-二恶烷的生物降解，因此，这些结果对于在存在氯代溶剂作为共污染物的地点选择 1,4-二恶烷生物修复策略具有重要意义。
